Safety Information

A place to relax and discuss flying topics.

Moderators: GAHorn, Karl Towle, Bruce Fenstermacher

Post Reply
voorheesh
Posts: 586
Joined: Tue Jan 04, 2005 5:22 am

Safety Information

Post by voorheesh »

A friend of mine had a recent experience in a Cessna 170B that needs to be mentioned here due to a serious safety issue that it raises. I am hoping he will address the association on this and give his version of a real success story but so far he has preferred to tell his story locally.

He has owned this aircraft for over 50 years and flies it regularly. Last February on a local flight he felt a sudden change in elevator effectiveness accompanied by a sound/bang. He soon realized his elevator had only partial effectiveness. He diverted to a nearby airport and made a successful landing. Investigation revealed that his right outboard elevator attach fitting was missing and the right elevator was supported by the trim tab rod and inboard torque tube. Further investigation of the hardware on his tail revealed several self locking nuts had worn out and were loose. He has since replaced this hardware and resumed flying.

This guy kept his head and did a superb job of handling an emergency that very easily could have resulted in a fatal accident. He told his story to local pilots recently and emphasized the need for careful preflights and the fact that 60 year old components are subject to unannounced failure. This nut is very difficult to see on the B model because it is shielded by elevator skin. This hardware can become dirty and hard to see. It is self locking as opposed to a cottered nut because it is designed to secure a bearing and not rotate with elevator movement. It may be advisable to have an IA check these nuts for security by applying a wrench to them during annuals. Old hardware should be upgraded. Years ago, I added small yellow paint stripes to hardware on my ship so you can detect loose nuts during preflight.

The last point this pilot made was that he had become compacent on his preflights. That struck home with me. You put the airplane in a hangar and you are the only one who flies it. What is the chance somthing will change in a week? Well this story is living proof that something very serious can happen. Again, this story is for everyone's benefit with the hope you will take a good look at your airplane's hardware. I am sure my friend will have more to say about this when he is ready.
bagarre
Posts: 2615
Joined: Thu Sep 30, 2010 11:35 pm

Re: Safety Information

Post by bagarre »

Do nylon self locking nuts have a recommended lifespan?
User avatar
blueldr
Posts: 4442
Joined: Thu May 02, 2002 3:16 am

Re: Safety Information

Post by blueldr »

On these old airplanes, some of the more obscure self locking nuts may well have less than our modern nylon locking material. I can remember that when I went to work for Lockheed, back before we entered WWII, I was facinated by "ESNA" lock nuts which I had never before seen. They had a red fiber locking part. They were only supposed to be used twice, and then discarded. I wouldn't be surprised if maybe some of our really old airplanes don't still have some of those older pieces of hardware still in place.
BL
User avatar
ghostflyer
Posts: 1390
Joined: Mon Apr 21, 2008 3:06 am

Re: Safety Information

Post by ghostflyer »

The life span on any hardware rests on useage and the enviroment that it lives in plus what the manufacturer recommends . If the hardware is in a hot , stressed area or its been on the aircraft a long time it requires a more detailed/frequent inspection. Hardware is so cheap and easy to obtain so if any my nuts and bolts look like their use by date ,its in the bin with them.
I have had a nasty experience with hardware when after landing I could feel a large knock under my feet and I had trouble keeping the aircraft straight. When in the hangar the aircraft had this list to port, and found the main attach bolt for the undercarriage leg sheared. The head had come off the bolt This bolt was replaced about 300 hrs ago. [they susposed to be replaced every 500 hrs I believe]. I cant recall having a heavy landing but I do a lot of landings in the rough stuff. So now key attachment areas get looked at very closely every 50 hrs [besides the 100 hrly]. As the aircraft operates in a salt enviroment ,corrosion is always being looked at also.
hilltop170
Posts: 3481
Joined: Sat May 06, 2006 6:05 pm

Re: Safety Information

Post by hilltop170 »

ghostflyer wrote: I have had a nasty experience with hardware when after landing I could feel a large knock under my feet and I had trouble keeping the aircraft straight. When in the hangar the aircraft had this list to port, and found the main attach bolt for the undercarriage leg sheared. The head had come off the bolt This bolt was replaced about 300 hrs ago. [they susposed to be replaced every 500 hrs I believe]. I cant recall having a heavy landing but I do a lot of landings in the rough stuff. So now key attachment areas get looked at very closely every 50 hrs [besides the 100 hrly]. As the aircraft operates in a salt enviroment ,corrosion is always being looked at also.
That is the best endorsement for the P-Ponk gearbox support, http://www.pponk.com/HTML%20PAGES/gldr.html I have ever heard. You're lucky the gear didn't twist out. Good thing you did a nice landing.
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
Robert Eilers
Posts: 652
Joined: Sat May 08, 2004 12:33 am

Re: Safety Information

Post by Robert Eilers »

How an airplane is used should really dictate how often important attach bolts and their lock nuts are replaced. I don't believe Cessna, when they designed the 170, ever intended for the 170 to be operated like a bush plane. Operating out of unimproved fields places loads on the important attach points that Cessna did not anticipate. The 170 IMHO was designed to be a NOVA not a Land Rover.
"You have to learn how to fall before you learn how to fly"
User avatar
n2582d
Posts: 2808
Joined: Mon Apr 29, 2002 4:58 am

Re: Safety Information

Post by n2582d »

voorheesh wrote:A friend of mine had a recent experience in a Cessna 170B that needs to be mentioned here due to a serious safety issue that it raises. I am hoping he will address the association on this and give his version of a real success story but so far he has preferred to tell his story locally.

He has owned this aircraft for over 50 years and flies it regularly. Last February on a local flight he felt a sudden change in elevator effectiveness accompanied by a sound/bang. He soon realized his elevator had only partial effectiveness. He diverted to a nearby airport and made a successful landing. Investigation revealed that his right outboard elevator attach fitting was missing and the right elevator was supported by the trim tab rod and inboard torque tube. Further investigation of the hardware on his tail revealed several self locking nuts had worn out and were loose. He has since replaced this hardware and resumed flying.

This guy kept his head and did a superb job of handling an emergency that very easily could have resulted in a fatal accident. He told his story to local pilots recently and emphasized the need for careful preflights and the fact that 60 year old components are subject to unannounced failure. This nut is very difficult to see on the B model because it is shielded by elevator skin. This hardware can become dirty and hard to see. It is self locking as opposed to a cottered nut because it is designed to secure a bearing and not rotate with elevator movement. It may be advisable to have an IA check these nuts for security by applying a wrench to them during annuals. Old hardware should be upgraded. Years ago, I added small yellow paint stripes to hardware on my ship so you can detect loose nuts during preflight.

The last point this pilot made was that he had become compacent on his preflights. That struck home with me. You put the airplane in a hangar and you are the only one who flies it. What is the chance somthing will change in a week? Well this story is living proof that something very serious can happen. Again, this story is for everyone's benefit with the hope you will take a good look at your airplane's hardware. I am sure my friend will have more to say about this when he is ready.
John Pugliese wrote up his experience of nearly losing his elevator in the 4th Quarter, 2012 issue of The 170 News. After reading that I decided to use castle nuts on the elevator and rudder hinge attach bolts. However, Cessna advises against using castellated nuts on the C-190/195 elevator attach bolts because of the chance that the bolts will rotate and wear the hinge attach fittings. As the 190/195 elevator is attached basically the same as the 170 I don't understand why Cessna didn't include the 170 series in the document I've attached below.
C-195 Elevator Hinge Attach.pdf
Model 190 & 195 Elevator Hinge Hardware Maintenance
(79.71 KiB) Downloaded 498 times
I think what is critical, whether one uses an AN365 self-locking nut or a AN310 castle nut, is that it is properly torqued as outlined in AC 43-13-1B page 7-298 ff. Don't forget to add drag torque to whatever torque value the nut is being torqued to. It used to be that AC 43-13-1 said that if one could hand tighten a self-locking nut onto a bolt then it should not be reused. In this revision they have table 7-2 "Minimum prevailing torque values for reused self-locking nuts." I like Voorheesh's idea of adding a painted yellow stripe to hardware. One could also use Torque Seal on these bolts/nuts to make it easier to tell if the bolt is turning with a frozen bearing or if it is inadequately torqued. I now plan on using MS17825 self-locking castle nuts on the elevator and rudder hinges.
Gary
User avatar
lowNslow
Posts: 1530
Joined: Mon Apr 22, 2002 4:20 pm

Re: Safety Information

Post by lowNslow »

n2582d wrote: I now plan on using MS17825 self-locking castle nuts on the elevator and rudder hinges.
Ahh, the old belt and suspenders approach. Very good.
Karl
'53 170B N3158B SN:25400
ASW-20BL
bagarre
Posts: 2615
Joined: Thu Sep 30, 2010 11:35 pm

Re: Safety Information

Post by bagarre »

lowNslow wrote:
n2582d wrote: I now plan on using MS17825 self-locking castle nuts on the elevator and rudder hinges.
Ahh, the old belt and suspenders approach. Very good.
Be sure to add some loc-tite for good measure ;)
User avatar
GAHorn
Posts: 20967
Joined: Fri Apr 12, 2002 8:45 pm

Re: Safety Information

Post by GAHorn »

Self-locking (Nylok type) nuts are specified in that location and they are NOT hard to see...if one actually LOOKS...which is what we should all be doing when we PRE_FLIGHT the airplane. That nut is quite visible.

Trouble is.... we owners flew it last time...and the time before that...and the time before that...and everything was just fine and all it's done is sit in the hangar since the last flight and there's no reason to suspect anything has changed since then..... GET THE IDEA????

DO PROPER AND THOROUGH PRE FLIGHT INSPECTIONS!
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
bagarre
Posts: 2615
Joined: Thu Sep 30, 2010 11:35 pm

Re: Safety Information

Post by bagarre »

I check my nuts before every flight.
User avatar
Ryan Smith
Posts: 1210
Joined: Tue Nov 25, 2008 4:26 am

Re: Safety Information

Post by Ryan Smith »

bagarre wrote:I check my nuts before every flight.
:lol:
User avatar
blueldr
Posts: 4442
Joined: Thu May 02, 2002 3:16 am

Re: Safety Information

Post by blueldr »

David Ross,

You must take into consideration that some of the C-170s are flown by members of the other gender.
BL
Post Reply